Typical micromachining process is capable of producing microstructures. The high capital investments required and the low processing yield limit the commercial applicability of this process. One reference teaches using gas to force the flow of molding material into a hollow cavity, and by keeping the continuous flow of a gas, a through pore is also formed within the molded material in the cavity. The thickness of the walls of microneedle formed in the reference is largely affected by the size of the hollow cavity and the flow conditions.